8.13. Configuring Parallel Replication

The replication stream within MySQL is by default executed in a
single-threaded execution model. Using Tungsten Replicator, the application
of the replication stream can be applied in parallel. This improves the
speed at which the database is updated and helps to reduce the effect of
slaves lagging behind the master which can affect application performance.
Parallel replication operates by distributing the events from the
replication stream from different database schemas in parallel on the
slave. All the events in one schema are applied in sequence, but events in
multiple schemas can be applied in parallel. Parallel replication will not
help in those situations where transactions operate across schema
boundaries.

Parallel replication supports two primary options:

Number of parallel channels — this configures the maximum number
of parallel operations that will be performed at any one time. The
number of parallel replication streams should match the number of
different schemas in the source database, although it is possible to
exhaust system resources by configuring too many. If the number of
parallel threads is less than the number of schemas, events are
applied in a round-robin fashion using the next available parallel
stream.

Parallelization type — the type of parallelization to be
employed. The disk method is the recommended solution.

Parallel replication can be enabled during installation by setting the
appropriate options during the initial configuration and installation. To
enable parallel replication after installation, you must configure each
host as follows: